The present invention relates generally to level sensors for use in underground tanks, and in particular but not by way of limitation, to a level sensor mechanism that provides for simple insertion of the sensor into the tank, and allows the level sensor mechanism to fixedly place a level sensor therein for accurate level sensing.
In typical underground tank storage systems, such as those used at fuel-filling stations, a tank fill pipe extends from ground level to a top portion of the tank. Within the tank fill pipe, a drop tube extends from ground level to a position near the bottom of the tank. There is a relatively small, set clearance between the tank fill pipe and the drop tube.
In the tank storage systems in which fuel is stored, the tanks may contain both fuel and water. These tanks are typically made of metal or ceramic materials, such as fiberglass. Level sensor mechanisms have been provided to detect both the fuel and water for many different reasons, such as ensuring an adequate fuel supply, tracking the amount of fuel in the tank, determining leakage in the tank, determining the amount of water in the tank, etc. Such level sensor mechanisms have included the use of floats and the like to either provide feedback based on the position of the floats, or to assist in maintaining a level sensor mechanism in proper position.
Other level sensor mechanisms have provided therewith shafts that extend to the bottom of the tank for stability, but are allowed to at least partially swing. These level sensor mechanisms at least partially swing through either the choice of materials provided on these level sensor mechanisms, which are typically metallic, through the use of buoyancy devices, such as floats and the like, or combinations thereof. These have proven problematic for several reasons.
First, these level sensor mechanisms may frictionally contact a surface of the tank. Over time, given that the liquid stored in the tank will repeatedly be drained and filled, the frictional contact will force a gradual wearing down of the tank, thereby exposing the environment to damage due to leakage of hazardous materials and the like stored therein. This problem is especially apparent when the level sensor mechanism has a metallic portion.
Second, the sensor inside of these level sensor mechanisms may provide aberrant feedback, given the movement of the level sensor mechanism over time. Re-calibration of theses sensors would therefore be required on a more frequent basis.
Third, the number of parts for these level sensor mechanisms may be excessive, especially when buoyancy devices are provided with the level sensor mechanisms. Because of the large number of tank storage systems, it is prohibitive to have intricate level sensor mechanisms that are costly.
Fourth, a majority of these level sensor mechanisms may have the additional problem of being difficult to install within a tank. Because these level sensor mechanisms typically have electrical wiring associated therewith, the level sensor mechanism is installed in an unused bung, which requires a disinterring of the tank and subsequent repair of the surface. This is both costly and disruptive.
To overcome these and other problems, the principles of the present invention provide for a level sensor mechanism for a storage tank. A conduit is provided having an upper portion and a lower portion. The conduit may be adapted to receive a cable therein, may be substantially rigid and adapted to resist deflection. A sensor assembly body is provided and adapted to locate a level sensor therein. The sensor assembly body may be located in fixed relation to said conduit, and may be rigidly composed and adapted to resist deflection.
A coupling member may be secured to said lower portion of said conduit, said coupling member fixedly securing said conduit to said sensor assembly body, said sensor assembly body being secured on said offset portion of said coupling member. The level sensor mechanism may thereby resist or eliminate deflection through the construction of the conduit, coupling member and sensor assembly body.